The pipeline industry utilizes various types of equipment positioned inside a pipe or pipeline for a number of purposes, including welding, bending and inspection of pipe integrity. Such equipment can include pipe bending mandrels to assist in bending of a pipe, X-ray and gamma-ray units used for non-destructive testing of field girth welds during pipeline construction, and other equipment used to facilitate maintenance and repairs such as video cameras for pipe inspection and plug-type pigs for pipeline shutdown and evaluation. The equipment can be moved to different locations inside a pipeline on a device which is commonly referred to as a pipeline pig.
Typically, an operator controls the movement of equipment, such as a mandrel, inside the pipe using a reach rod. The reach rod is connected to the equipment and extends out the open end of the pipeline. An operator positioned near the opening of the pipe controls the positioning and functioning of the equipment through the reach rod. In order to position the piece of equipment within the pipeline at the appropriate location, the equipment inside the pipeline typically includes a transmitter which transmits an electromagnetic signal from inside the pipe to outside the pipe. Low frequency transmitters which are used to track pipeline pigs and equipment are well known in the art. However, present systems transmit the electromagnetic signals from inside the pipe to a receiver located at a point outside the pipe. The location of the equipment on the pipeline pig is then determined with reference to the receiver. The operator can also position the equipment, by use of the reach rod, at the appropriate location. Once the equipment is in the correct location in a pipe, the operator can use control lines that extend through the reach rod to control the functioning of the equipment as required.
Present systems used for locating equipment inside a pipe and controlling the functioning of this equipment have disadvantages which include the increased expense associated with using and maintaining the reach rod. Further, present systems require that the operator of the equipment be located near the point where the reach rod enters the pipe. Another drawback of these reach rod systems is the limited length of travel of this equipment within the pipe as determined by the length of the reach rod.